Project III: Child and Environmental Predictors of Communication Success by beginning VOCA users. The proposed research systematically extends the investigator's research on successful communication, including success following communication breakdowns, to the population of preschool children learning to communicate with VOCAs. We will be investigating parameters surrounding successful communication at the cusp of beginning symbolic communication. The investigator's recently completed research showed that preschool -age children frequently experienced communication breakdowns during the course of natural conversations with their mothers. Participants'skills in repairing these breakdowns were related to their extant expressive and receptive communication skills and to their mothers'responsivity. Preschool children learning to communicate with VOCAs appear particularly vulnerable to communication breakdowns due to partner familiarity with VOCAs and access to VOCAs across environments. The purpose of the proposed research is to identify specific child and environmental predictors of successful communication and other indices of communication growth for 50 preschool-age children learning to communicate with VOCAs. We hypothesize that the specific variables we have found to predict child communicative success in our past research will also predict success by children learning VOCA communication. In addition, we hypothesize that environmental variables including how VOCAs are incorporated into classroom instruction and home activities will relate to children's successful communication. These hypotheses will be investigated by measuring children's communication rate, vocabulary growth both in VOCA symbol selection and speech vocabulary, and measuring proportions of successful communication overtime. Success will be determined by applying our operational definition that relies on both child communication acts and partner responses to these communication acts. Growth curve modeling will be used to determine patterns of growth over a 2 year period by children with differing abilities at the start of intervention, and who are experiencing different amounts of environmental support for AAC in their classroomenvironments.